1. Field of the Invention
This invention relates to an improvement of an apparatus for pneumatically transporting powdery or granular materials, and more particularly to the apparatus comprising a material supply unit, a material receiver unit and a transport pipeline in which a spherical secondary transport medium with an outside diameter slightly less than the inside diameter of the transport pipeline is fed one by one just behind the materials to be transported, whereby transporting intermittently the materials together with the spherical secondary transport medium from the material supply unit through the transport pipeline to the material receiver unit at a relatively low speed by the action of fluid under pressure.
2. Description of the Prior Art
There has been known the pneumatic transportation system in which compressed air is introduced into a pressure chamber so as to transport a powdery or granular material through a transport pipeline. In this case, the powdery or granular materials supplied into the system can be continuously transported by floating it on airflow caused in the transport pipeline. However, such system is allowed to perform the pneumatic transportation of the materials in the transport pipeline only when the back pressure therein is lower than pneumatics supplied thereinto, and therefore is not adapted for the transportation in a large level thereof and of materials difficult to be transported, that is; materials which tend to clog the transport pipeline. Further, the compressed air employed in the above-mentioned conventional system is generally required to be kept at a relatively high speed such as, for example, 20 to 40 m/sec. Therefore, such system is disadvantageous in that powdery or granular materials are sometimes broken, or the transport pipeline tends to be worn away. On the contrary, if the speed of the compressed air or fluid under pressure is further reduced, the powdery or granular materials become unable to float or suspend on the air current so as to adhere to or deposit on the bottom part of the transport pipeline. If the speed of the compressed air is reduced much more, the powdery or granular material will accumulate gradually within the transport pipeline to form a plug, and finally clog the transport pipeline.
According to our investigations, as for the appropriate prior art most pertinent to the present invention, there is a system referred to as "plug transportation" in which the material to be transported is formed in a plug shape in the transport pipeline so as to permit the material to be transported through the latter. However, the above-mentioned prior art plug transportation system could be achieved under extremely limited conditions, since such transportation system depends largely on various factors such as the physical property of the material to be transported, the inside diameter of the transport pipeline, the amount of the compressed air and the method of flowing the latter etc.